Creature Girls: a Hands-On Field Journal in Another World Vol. 14 (manga)

ONCE A NERD, NOW A DEMON LORD--AND MASTER OF ALL HE SURVEYS! Thanks to his scientific knowledge and tremendous martial arts expertise, Taishi Oritsue has transformed the Midori goblin clan into a dreadful fighting force worthy of being called "the Demon Lord's army." Despite living in the horrifying Death Mountains, they live a comfortable life with amenities--and orgies--the outside world can only dream of. Yet they may have met an unexpectedly strong opponent in the forces of the human Republic. Their tenacious soldiers are trained by a man who practices the very same Earth-world martial arts as Oritsue himself!